As the components required to build a computer system have reduced in size, new categories of computer systems have emerged. One of the new categories of computer systems is the "palmtop" computer system. A palmtop computer system is a computer that is small enough to be held in the hand of a user. Most palmtop computer systems are used to implement various Personal Information Management (PIM) applications such as an address book, a daily organizer, and electronic notepads.
Since palmtop computer systems are very small, keyboards are generally not efficient input devices. Palmtop computers with keyboards have keyboards that are so small that a user cannot touch-type. Furthermore, to use a keyboard a user must either place the palmtop computer system down onto a flat surface so the user can type with both hands or hold the palmtop computer system with two hands and type with thumbs only.
Instead of using a keyboard, many palmtop computers employ a pen and a digitizer pad as an input system. The pen and digitizer pad combination works well for palmtop computers since the arrangement allows a user to hold the palmtop computer system in one hand while writing with the pen onto the digitizer pad with the other hand.
A number of palmtop computer systems that rely on the pen and digitizer pad combination as the primary means of input have been introduced to the market. Most of these pen-based palmtop computer systems provide some type of handwriting recognition system whereby the user can write words and letters on the digitizer pad with a stylus. The palmtop computer system then converts the user's handwriting into a machine readable format such as ASCII code. Examples of pen-based palmtop computer systems that provide handwriting recognition include the Apple.RTM. Newton.RTM. and the Tandy.RTM. Zoomer.TM..
Consumer acceptance of pen based palmtop computer systems has been limited due to the poor performance of handwriting recognition systems. When a human reads a handwritten message, the human uses various clues to decipher the handwriting such as the known spelling of words, the known subject of the message, the writer's character writing style, and knowledge of English grammar. Since it is very difficult to teach a computer system all these subtle handwriting recognition heuristics, most handwriting recognition systems only rely on the writer's input strokes and a dictionary of common words. Using such limited information, such handwriting recognition systems often yield inaccurate results.
One method of simplifying the task of handwriting recognition is to divide the recognition task into identifying individual characters. This method is employed by the recognition system disclosed in the patent application titled "Multiple Pen Stroke Character Set and Handwriting Recognition System With Immediate Response" filed by Hawkins, et al. on Jul. 1, 1994, having Ser. No. 08/270,025. Using the immediate character recognition system disclosed in the Hawkins reference, a user can write as fast he wants and achieve nearly 100% recognition. However, systems constructed according to the Hawkins reference can only recognize a limited number of characters without introducing confusing "mode change" strokes. It would therefore be desirable to have a computer system with a character recognition system that can recognize a large number of different characters with less effort on the user's part (i.e., fewer "mode change" strokes).